i was thinking of using all 14 pins rather than multiplex?
then i can control each pin with a transistor? ( switch ground)
I agree, if this is for outdoor use, you need maximum brightness. That means no multiplexing.
If you are building these displays from strips, you can choose to make them common cathode or common anode.
If you make them common anode it will be easier.
With common anode, you can simply use an ordinary npn transistor for each segment (between the segment -ve and ground). BC337 would be ok for example. The Arduino pins (or shift register pins) can drive the transistor bases directly with 1K resistors to limit the base current. Alternatively use 2 x tpic6a595 high-current shift registers. The "a" variant can sink up to 350mA per pin.
With common cathode, its slightly trickier. You can use ordinary pnp transistors like BC327, between +12V and each segment +ve. But you can't drive the pnp bases directly with Arduino/shift register pins. They would be damaged by the 12V supply. So you would need an npn to pull each pnp base down and 10K to pull the pnp base up to 12V. Again, use 1K to limit the pnp base current and 4K7 to limit the npn base current. Alternatively use 2 x ULN2003/2803/tpic6c595 instead of the npn.
Your estimate of 250mA per segment may be too high. 30cm segments, assuming ordinary 60 leds/metre srtips, would need 60 * 0.3 * 20 / 3 = 120mA. Were you thinking of two parallel strips for each segment?